mirror of
https://github.com/ecency/ecency-mobile.git
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462 lines
12 KiB
C++
462 lines
12 KiB
C++
/*
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* Copyright 2016 Facebook, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <cstdint>
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#include <cstring>
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#include <string>
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#include <tuple>
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#include <type_traits>
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#include <utility>
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#include <folly/ApplyTuple.h>
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#include <folly/Bits.h>
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#include <folly/SpookyHashV1.h>
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#include <folly/SpookyHashV2.h>
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/*
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* Various hashing functions.
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*/
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namespace folly { namespace hash {
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// This is a general-purpose way to create a single hash from multiple
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// hashable objects. hash_combine_generic takes a class Hasher implementing
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// hash<T>; hash_combine uses a default hasher StdHasher that uses std::hash.
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// hash_combine_generic hashes each argument and combines those hashes in
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// an order-dependent way to yield a new hash.
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// This is the Hash128to64 function from Google's cityhash (available
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// under the MIT License). We use it to reduce multiple 64 bit hashes
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// into a single hash.
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inline uint64_t hash_128_to_64(const uint64_t upper, const uint64_t lower) {
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// Murmur-inspired hashing.
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const uint64_t kMul = 0x9ddfea08eb382d69ULL;
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uint64_t a = (lower ^ upper) * kMul;
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a ^= (a >> 47);
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uint64_t b = (upper ^ a) * kMul;
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b ^= (b >> 47);
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b *= kMul;
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return b;
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}
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// Never used, but gcc demands it.
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template <class Hasher>
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inline size_t hash_combine_generic() {
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return 0;
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}
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template <
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class Iter,
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class Hash = std::hash<typename std::iterator_traits<Iter>::value_type>>
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uint64_t hash_range(Iter begin,
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Iter end,
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uint64_t hash = 0,
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Hash hasher = Hash()) {
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for (; begin != end; ++begin) {
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hash = hash_128_to_64(hash, hasher(*begin));
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}
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return hash;
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}
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inline uint32_t twang_32from64(uint64_t key);
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template <class Hasher, typename T, typename... Ts>
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size_t hash_combine_generic(const T& t, const Ts&... ts) {
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size_t seed = Hasher::hash(t);
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if (sizeof...(ts) == 0) {
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return seed;
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}
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size_t remainder = hash_combine_generic<Hasher>(ts...);
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/* static */ if (sizeof(size_t) == sizeof(uint32_t)) {
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return twang_32from64((uint64_t(seed) << 32) | remainder);
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} else {
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return static_cast<size_t>(hash_128_to_64(seed, remainder));
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}
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}
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// Simply uses std::hash to hash. Note that std::hash is not guaranteed
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// to be a very good hash function; provided std::hash doesn't collide on
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// the individual inputs, you are fine, but that won't be true for, say,
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// strings or pairs
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class StdHasher {
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public:
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template <typename T>
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static size_t hash(const T& t) {
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return std::hash<T>()(t);
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}
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};
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template <typename T, typename... Ts>
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size_t hash_combine(const T& t, const Ts&... ts) {
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return hash_combine_generic<StdHasher>(t, ts...);
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}
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//////////////////////////////////////////////////////////////////////
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/*
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* Thomas Wang 64 bit mix hash function
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*/
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inline uint64_t twang_mix64(uint64_t key) {
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key = (~key) + (key << 21); // key *= (1 << 21) - 1; key -= 1;
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key = key ^ (key >> 24);
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key = key + (key << 3) + (key << 8); // key *= 1 + (1 << 3) + (1 << 8)
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key = key ^ (key >> 14);
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key = key + (key << 2) + (key << 4); // key *= 1 + (1 << 2) + (1 << 4)
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key = key ^ (key >> 28);
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key = key + (key << 31); // key *= 1 + (1 << 31)
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return key;
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}
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/*
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* Inverse of twang_mix64
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*
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* Note that twang_unmix64 is significantly slower than twang_mix64.
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*/
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inline uint64_t twang_unmix64(uint64_t key) {
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// See the comments in jenkins_rev_unmix32 for an explanation as to how this
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// was generated
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key *= 4611686016279904257U;
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key ^= (key >> 28) ^ (key >> 56);
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key *= 14933078535860113213U;
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key ^= (key >> 14) ^ (key >> 28) ^ (key >> 42) ^ (key >> 56);
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key *= 15244667743933553977U;
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key ^= (key >> 24) ^ (key >> 48);
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key = (key + 1) * 9223367638806167551U;
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return key;
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}
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/*
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* Thomas Wang downscaling hash function
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*/
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inline uint32_t twang_32from64(uint64_t key) {
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key = (~key) + (key << 18);
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key = key ^ (key >> 31);
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key = key * 21;
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key = key ^ (key >> 11);
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key = key + (key << 6);
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key = key ^ (key >> 22);
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return (uint32_t) key;
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}
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/*
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* Robert Jenkins' reversible 32 bit mix hash function
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*/
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inline uint32_t jenkins_rev_mix32(uint32_t key) {
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key += (key << 12); // key *= (1 + (1 << 12))
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key ^= (key >> 22);
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key += (key << 4); // key *= (1 + (1 << 4))
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key ^= (key >> 9);
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key += (key << 10); // key *= (1 + (1 << 10))
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key ^= (key >> 2);
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// key *= (1 + (1 << 7)) * (1 + (1 << 12))
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key += (key << 7);
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key += (key << 12);
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return key;
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}
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/*
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* Inverse of jenkins_rev_mix32
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*
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* Note that jenkinks_rev_unmix32 is significantly slower than
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* jenkins_rev_mix32.
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*/
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inline uint32_t jenkins_rev_unmix32(uint32_t key) {
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// These are the modular multiplicative inverses (in Z_2^32) of the
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// multiplication factors in jenkins_rev_mix32, in reverse order. They were
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// computed using the Extended Euclidean algorithm, see
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// http://en.wikipedia.org/wiki/Modular_multiplicative_inverse
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key *= 2364026753U;
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// The inverse of a ^= (a >> n) is
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// b = a
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// for (int i = n; i < 32; i += n) {
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// b ^= (a >> i);
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// }
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key ^=
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(key >> 2) ^ (key >> 4) ^ (key >> 6) ^ (key >> 8) ^
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(key >> 10) ^ (key >> 12) ^ (key >> 14) ^ (key >> 16) ^
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(key >> 18) ^ (key >> 20) ^ (key >> 22) ^ (key >> 24) ^
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(key >> 26) ^ (key >> 28) ^ (key >> 30);
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key *= 3222273025U;
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key ^= (key >> 9) ^ (key >> 18) ^ (key >> 27);
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key *= 4042322161U;
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key ^= (key >> 22);
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key *= 16773121U;
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return key;
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}
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/*
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* Fowler / Noll / Vo (FNV) Hash
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* http://www.isthe.com/chongo/tech/comp/fnv/
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*/
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const uint32_t FNV_32_HASH_START = 2166136261UL;
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const uint64_t FNV_64_HASH_START = 14695981039346656037ULL;
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inline uint32_t fnv32(const char* s,
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uint32_t hash = FNV_32_HASH_START) {
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for (; *s; ++s) {
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hash += (hash << 1) + (hash << 4) + (hash << 7) +
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(hash << 8) + (hash << 24);
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hash ^= *s;
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}
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return hash;
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}
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inline uint32_t fnv32_buf(const void* buf,
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size_t n,
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uint32_t hash = FNV_32_HASH_START) {
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// forcing signed char, since other platforms can use unsigned
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const signed char* char_buf = reinterpret_cast<const signed char*>(buf);
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for (size_t i = 0; i < n; ++i) {
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hash += (hash << 1) + (hash << 4) + (hash << 7) +
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(hash << 8) + (hash << 24);
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hash ^= char_buf[i];
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}
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return hash;
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}
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inline uint32_t fnv32(const std::string& str,
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uint32_t hash = FNV_32_HASH_START) {
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return fnv32_buf(str.data(), str.size(), hash);
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}
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inline uint64_t fnv64(const char* s,
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uint64_t hash = FNV_64_HASH_START) {
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for (; *s; ++s) {
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hash += (hash << 1) + (hash << 4) + (hash << 5) + (hash << 7) +
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(hash << 8) + (hash << 40);
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hash ^= *s;
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}
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return hash;
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}
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inline uint64_t fnv64_buf(const void* buf,
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size_t n,
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uint64_t hash = FNV_64_HASH_START) {
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// forcing signed char, since other platforms can use unsigned
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const signed char* char_buf = reinterpret_cast<const signed char*>(buf);
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for (size_t i = 0; i < n; ++i) {
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hash += (hash << 1) + (hash << 4) + (hash << 5) + (hash << 7) +
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(hash << 8) + (hash << 40);
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hash ^= char_buf[i];
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}
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return hash;
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}
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inline uint64_t fnv64(const std::string& str,
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uint64_t hash = FNV_64_HASH_START) {
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return fnv64_buf(str.data(), str.size(), hash);
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}
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/*
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* Paul Hsieh: http://www.azillionmonkeys.com/qed/hash.html
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*/
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#define get16bits(d) folly::loadUnaligned<uint16_t>(d)
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inline uint32_t hsieh_hash32_buf(const void* buf, size_t len) {
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// forcing signed char, since other platforms can use unsigned
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const unsigned char* s = reinterpret_cast<const unsigned char*>(buf);
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uint32_t hash = static_cast<uint32_t>(len);
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uint32_t tmp;
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size_t rem;
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if (len <= 0 || buf == 0) {
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return 0;
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}
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rem = len & 3;
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len >>= 2;
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/* Main loop */
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for (;len > 0; len--) {
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hash += get16bits (s);
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tmp = (get16bits (s+2) << 11) ^ hash;
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hash = (hash << 16) ^ tmp;
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s += 2*sizeof (uint16_t);
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hash += hash >> 11;
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}
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/* Handle end cases */
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switch (rem) {
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case 3:
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hash += get16bits(s);
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hash ^= hash << 16;
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hash ^= s[sizeof (uint16_t)] << 18;
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hash += hash >> 11;
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break;
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case 2:
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hash += get16bits(s);
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hash ^= hash << 11;
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hash += hash >> 17;
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break;
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case 1:
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hash += *s;
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hash ^= hash << 10;
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hash += hash >> 1;
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}
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/* Force "avalanching" of final 127 bits */
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hash ^= hash << 3;
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hash += hash >> 5;
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hash ^= hash << 4;
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hash += hash >> 17;
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hash ^= hash << 25;
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hash += hash >> 6;
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return hash;
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};
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#undef get16bits
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inline uint32_t hsieh_hash32(const char* s) {
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return hsieh_hash32_buf(s, std::strlen(s));
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}
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inline uint32_t hsieh_hash32_str(const std::string& str) {
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return hsieh_hash32_buf(str.data(), str.size());
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}
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//////////////////////////////////////////////////////////////////////
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} // namespace hash
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template<class Key, class Enable = void>
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struct hasher;
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struct Hash {
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template <class T>
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size_t operator()(const T& v) const {
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return hasher<T>()(v);
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}
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template <class T, class... Ts>
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size_t operator()(const T& t, const Ts&... ts) const {
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return hash::hash_128_to_64((*this)(t), (*this)(ts...));
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}
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};
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template<> struct hasher<int32_t> {
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size_t operator()(int32_t key) const {
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return hash::jenkins_rev_mix32(uint32_t(key));
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}
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};
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template<> struct hasher<uint32_t> {
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size_t operator()(uint32_t key) const {
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return hash::jenkins_rev_mix32(key);
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}
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};
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template<> struct hasher<int64_t> {
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size_t operator()(int64_t key) const {
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return static_cast<size_t>(hash::twang_mix64(uint64_t(key)));
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}
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};
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template<> struct hasher<uint64_t> {
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size_t operator()(uint64_t key) const {
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return static_cast<size_t>(hash::twang_mix64(key));
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}
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};
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template<> struct hasher<std::string> {
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size_t operator()(const std::string& key) const {
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return static_cast<size_t>(
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hash::SpookyHashV2::Hash64(key.data(), key.size(), 0));
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}
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};
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template <class T>
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struct hasher<T, typename std::enable_if<std::is_enum<T>::value, void>::type> {
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size_t operator()(T key) const {
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return Hash()(static_cast<typename std::underlying_type<T>::type>(key));
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}
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};
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template <class T1, class T2>
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struct hasher<std::pair<T1, T2>> {
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size_t operator()(const std::pair<T1, T2>& key) const {
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return Hash()(key.first, key.second);
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}
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};
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template <typename... Ts>
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struct hasher<std::tuple<Ts...>> {
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size_t operator() (const std::tuple<Ts...>& key) const {
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return applyTuple(Hash(), key);
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}
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};
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// recursion
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template <size_t index, typename... Ts>
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struct TupleHasher {
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size_t operator()(std::tuple<Ts...> const& key) const {
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return hash::hash_combine(
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TupleHasher<index - 1, Ts...>()(key),
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std::get<index>(key));
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}
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};
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// base
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template <typename... Ts>
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struct TupleHasher<0, Ts...> {
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size_t operator()(std::tuple<Ts...> const& key) const {
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// we could do std::hash here directly, but hash_combine hides all the
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// ugly templating implicitly
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return hash::hash_combine(std::get<0>(key));
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}
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};
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} // namespace folly
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// Custom hash functions.
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namespace std {
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// Hash function for pairs. Requires default hash functions for both
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// items in the pair.
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template <typename T1, typename T2>
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struct hash<std::pair<T1, T2> > {
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public:
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size_t operator()(const std::pair<T1, T2>& x) const {
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return folly::hash::hash_combine(x.first, x.second);
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}
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};
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// Hash function for tuples. Requires default hash functions for all types.
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template <typename... Ts>
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struct hash<std::tuple<Ts...>> {
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size_t operator()(std::tuple<Ts...> const& key) const {
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folly::TupleHasher<
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std::tuple_size<std::tuple<Ts...>>::value - 1, // start index
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Ts...> hasher;
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return hasher(key);
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}
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};
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} // namespace std
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